1. Field of the Invention
The present invention generally relates to a signal processing circuit, and more particularly, to a signal processing circuit outputting a signal corresponding to a quality of a digitized input signal, such as a wobble signal.
2. Description of the Related Art
Conventionally, a wobble is formed on a recording optical disk, such as a CD or a DVD, in which a track on/from which information is recorded/reproduced wobbles in radial directions. An optical disk device comprises an optical head that opposes the surface of the disk upon the disk being mounted on the optical disk device. The optical head projects a laser light on the disk so as to record information on the disk, and also receives a reflected light from the disk so as to output a reproduction signal corresponding to information recorded on the disk. Information reproduced by the optical head includes a signal originating from the wobble formed on the disk (hereinafter referred to as a wobble signal). The optical disk device extracts the wobble signal from the information reproduced by the optical head, and according to this wobble signal, performs an obtainment of address information representing a disk position, a drive control of a spindle motor revolving the disk, or a generation of a reference clock, etc.
Thus, in order to cause the optical disk device to function properly, a wobble signal that accords properly to the wobble formed on the optical disk needs to be generated from the wobble. That is, if a wobble signal is not properly and surely reproduced according to the wobble of the disk, it may happen that a recording to the disk is interrupted, and further that the recording becomes unable to resume. Accordingly, to avoid these inconveniences, it is important to monitor a quality of the wobble signal generated from the wobble of the optical disk.
The quality of the wobble signal is found aggravated when a detection error of the address information, etc. included in the wobble signal occurs. Accordingly, it is possible to judge the quality of the wobble signal according to the presence of the detection error of the address information.
However, the detection error of the address information based on the wobble signal does not occur until the quality of the wobble signal becomes aggravated considerably. Accordingly, when the detection error of the address information is detected, it may already happen that a recording to the disk is interrupted, and further that the recording becomes unable to resume, due to the aggravation of the quality of the wobble signal. Therefore, in consideration of this point, it is not appropriate to judge the quality of the wobble signal according to whether or not the detection error of the address information occurs.